1. Field of the Invention
The present invention relates to a pressure-sensitive recording sheet which senses the pressure applied thereon by the change in color density, and an occlusion pressure detecting sheet used by a dentist for the measurement of the occlusion pressure and condition of a patient.
2. Prior Art
A pressure-sensitive recording sheet composed of a support sheet coated with a color developer and a color former overcoated on the color developer layer has been known in the art (reference should be made, for example, to Japanese Patent Publication Nos. 24852/1982 (corresponding to U.S. Pat. No. 4,132,112) and 16654/1984 (corresponding to U.S. Pat. No. 4,002,060)).
However, this known pressure-sensitive recording sheet has a disadvantage that the pressure applied thereon cannot be sensed precisely when the color former is wetted with water. To overcome such a disadvantage, it has been conceived to cover the sheet with a transparent waterproof sheet. For example, Japanese Utility Model Publication No. 8166/1970 discloses a structure wherein a waterproof layer is formed by laminating a polyethylene layer or by coating an emulsion of a vinylidene chloride copolymer on one face of a transparent paper sheet (serving as a support), and microcapsules of a color former are coated on the other face of the transparent paper sheet, the sheet being bent to form an envelope such that the face coated with the microcapsules of the color former spreads as the interior faces, between which a proper leaf of intermediate or underlying paper coated with a color developer is contained, followed by sealing the outer periphery of the envelope by the use of an adhesive.
Unexamined Japanese Patent Publication Nos. 68513/1977 and 24314/1976 disclose an alternative structure wherein protective layers are laminated over the pressure-detecting faces of the recording sheet so that the sheet structure has the waterproof property.
However, in the prior art structure wherein one face of a transparent paper sheet is protected by a waterproof layer while the other face being applied with the microcapsule layer and an envelope is formed by the such composite laminated structure followed by sealing of the outer periphery of the envelope, the microcapsule layer is interposed, together with the adhesive, between the folded two layers of the transparent paper sheet at the marginal portions of the envelope. As the result, adhesion of the entire envelope structure becomes unreliable. In addition, tight adhesion between the transparent paper sheet and the intermediate or underlying sheet cannot be expected, and there is also another problem of delamination when it is in use.
The other prior art technique of laminating, by heat seal, the protection layer over the recording sheet has a disadvantage that the property of the recording sheet is deteriorated by the application of heat, leading to reduction in color developing property.
On the other hand, in the field of dental treatment, carbon paper has been widely used to know the occlusion condition of the teeth of a patient. Carbon paper is inserted between the upper and lower dental arches of the patient; and as the patient bites strongly to occulude the upper and lower teeth, carbon particles adhere on the occlusal surface at the portions where the upper and lower teeth are abutted. The dentist can diagnose the occlusion condition of the teeth of the patient by observing the positions and areas of the portions to which carbon particles stick.
However, by this prior art of using carbon paper, it is merely possible to detect the portions where the upper and lower teeth abut with each other, and precise detection of occlusion pressure cannot be done by the use of carbon paper. Under such circumstance, the dentist should estimate the occlusion pressure by observing the sticking condition of carbon particles, leading to the problem that the precise diagnosis of occlusion condition of the teeth of the patient cannot be made, leading to difficulty in determination of subsequent dental treatment course.
Another problem of the prior art, in which carbon paper is used, is that it becomes necessary to impinge the upper and lower teeth for plural times or to rub the portions of carbon paper which contact teeth by the tooth tips, for example, by offseting the upper and lower jaws and then sliding them laterally.
The prior art technology has another problem that the dentist must precisely position the detecting sheet, such as carbon paper, by looking into the oral cavity of the patient since there is provided no means for precisely positioning the detecting sheet so as to know the portions, at which upper and lower teeth contact or abut with each other. This leads to the problem that the operation efficiency is lowered.